Microtunnelling: Optimising Low-Emission Construction of Buried Utility Infrastructure (MOLE)

Building and construction are responsible for 39% of all carbon emissions in the world [1]. Carbon emissions released before the built asset is used, referred to as 'embodied carbon' (EC), will be responsible for more than half of the entire carbon footprint of new construction between now and 2050. A substantial amount of new buried infrastructure is required in the UK alone [3]. As such, the development of sustainable construction techniques is essential.



This project focuses on the development, testing, optimization, and validation of novel low carbon microtunneling (MT). MT is an increasingly popular trenchless, remote-controlled construction method for the provision of underground utility tunnels and pipelines typically 0.5 m to 4 m in diameter [2]. As such, this project falls within the EPSRC Infrastructure Research Area.

Traditionally, open-cut construction (where a trench is dug from the ground surface and the pipeline is laid within the trench), has been used. Trenchless construction techniques have been shown to deliver up to 84% reduction in carbon emissions compared to open-cut construction [4]. However, the EC associated with trenchless construction remains unacceptably high (~22 tonnes of CO2 per km [5]). Existing research relates to alternative trenchless technologies rather than MT. This lack of research inhibits optimisation based on environmental impact, rather than solely on project cost, so there is an urgent need to quantify and track the EC associated with UK MT.

The research will aim to deliver the underpinning engineering science for next generation critical buried infrastructure using low-carbon materials and MT operations. Specifically, this project will directly tackle the following obstacles towards decarbonising the delivery of buried infrastructure: a) uncertainty surrounding the EC associated with the different construction stages and activities for MT, b) out-dated and overly conservative design guidelines, and c) commonly accepted high-EC reinforced concrete pipe designs.

To realise these aims, the following measurable objectives will be achieved:

(1) Perform an EC LCA to establish current baseline EC levels associated with MT. LCA will allow a quantitative assessment of the EC associated with different MT construction stages and operations to provide unprecedented insight into high-carbon activities. This is novel as existing literature has focused on alternative trenchless techniques.

(2) Develop a framework to infer the loading history of MT jacking pipes intelligently and accurately by developing novel measurement techniques deployed on site.

(3) Develop and experimentally test novel low-carbon MT pipes designed to safely withstand the measured load histories. Establish and validate new design methodologies for MT pipes.

(4) Develop, instrument, and deploy a novel conceptual instrumented smart pipe on live construction sites, working with collaborators Tracey Concrete and Ward and Burke Construction, to further test, validate and optimize the development of new MT design guidelines.

(5) Evaluate the success of the project through carbon saving measurements.

References: [1] Global Status Report (2017), UN Environ. & Int. Energy Agency. [2] Phillips, B.M. et al. (2019) doi: 10.1680/icsic.64669.457. [3] National Infrastructure Commission (2017), Congestion, Capacity, Carbon: Priorities for national infrastructure. [4] Tavakoli, R. et al. (2017) doi: 10.1061/ 9780784480892.005. [5] Nandyala, V.K. et al. (2019) doi: 10.1061/9780784482506.007.